1. Field
The present disclosure relates to a 3-dimensional (cubic) displaying apparatus, and more particularly, to a glasses-free (or, autostereoscopic) 3-dimensional displaying apparatus using line light sources, which may minimize the deterioration of quality of a 3-dimensional image caused by the change of distance from the 3-dimensional displaying apparatus by an observer.
2. Description of the Related Art
As the demand for displaying apparatuses capable of 3-dimensional images to give an actual stereoscopic effect not realized by a 2-dimensional image is increasing, displaying apparatuses capable of expressing 3-dimensional images are being developed.
While staring at an object present in the natural world with right and left eyes, a human may have a stereoscopic feeling since both eyes have different viewing angles. Image information of objects with slightly different viewing angles forms an image on the retina through the right and left eyes, and the information of the formed stereo vision is transferred through the optic nerve to the brain to give a stereoscopic effect.
In detail, a 3-dimensional image is generally formed by means of the stereo vision principle through both eyes. Here, there has been proposed a displaying apparatus which may exhibit a cubic image by using the binocular disparity occurring due to the face that both eyes are spaced apart by about 65 mm. To describe the implementation of 3-dimensional images in more detail, right and left eyes looking the displaying apparatus see different 2-dimensional images. If two images are transferred through the retina to the brain, the brain fuses two images exactly to regenerate the original 3-dimensional image in depth and realistically, and this phenomenon is generally called stereography.
In a conventional glass-free 3-dimensional displaying apparatus, a parallax separating unit is disposed at the front of an existing 2-dimensional displaying apparatus to transmit different parallax images to the left eye and the right eye of an observer so that the observer may receive an actual 3-dimensional image. The parallax separating unit used for giving such a stereoscopic effect may be a parallax barrier plate or a lenticular lens sheet. The example where a parallax barrier plate is used as the parallax separating unit to implement a 3-dimensional image is shown in FIG. 1.
FIG. 1 shows an implementing principle of a 3-dimensional image information displaying device with two viewing zones as a conventional example. Referring to FIG. 1, the conventional 3-dimensional image information displaying device 100 with two viewing zones includes a general 2-dimensional display panel 110 and a parallax barrier plate 130 disposed to be spaced apart from the front surface of the display panel 110. The pixels formed on the display panel 110 are composed of left eye image pixels 13 and right eye image pixels 15. The parallax barrier plate 130 has an open region and a barrier region, and the image information emitting from the left eye image pixel 13 and the right eye image pixel 15 passes through the open region and does not pass through the barrier region. The image information passing through the open region reaches a designed observation distance to be focused thereat. Among locations of an observer in the designed observation distance, the location A allows only the image information of the left eye to be observed, and the location B allows only the image information of the right eye to be observed.
However, such a method of displaying a 3-dimensional image by means of parallax separation using the parallax barrier plate 130 has several problems which should be solved. First, in a case where the eyes move horizontally so that the left eye is located at the location D and the right eye is located at the location E, the image information emitting from the left eye image pixel 13 and the right eye image pixel 15 are simultaneously applied to the left eye and the right eye as shown by dotted lines in the figure. As a result, it is impossible to see a clear 3-dimensional image. This phenomenon is called that a crosstalk occurs between viewing zones.
Second, in a case where the observer moves horizontally so that the left eye of the observer is located at the location B and the right eye is located at the location C, the left eye watches the image information emitting from the right eye image pixel 15, and the right eye watches the image information emitting from the left eye image pixel 13. As a result, a reversed stereovision is obtained, and it is impossible to watch normal 3-dimensional image information.
Third, the image in the corresponding viewing zone does not have regular brightness, and when the eyes move horizontally, the brightness of the image changes. This problem will be described in detail with reference to FIG. 2.
FIG. 2 is a light distribution graph between viewing zones of a 3-dimensional image obtained using a conventional parallax separating unit. Here, the horizontal axis represents a horizontal location at an observation distance, and the vertical axis represents the intensity of light. Referring to FIG. 2, in a case where the left eye and the right eye respectively located at a first viewing zone (shown with a solid line) and a second viewing zone (shown with a dotted line) move right or left in the horizontal direction, the brightness of the corresponding image decreases, and a crosstalk problem also occurs since the information of the image is mixed with the information of a neighboring viewing zone.
In addition, if the observer becomes closer or farther by just 5% of the optimum distance from the display, the viewing zone separation greatly deteriorates, compared with the separation at the optimum distance (see FIGS. 4A to 4D, where the crosstalk increases).
The above description is based on the example where the parallax barrier plate is used as the parallax separation unit, but the same problem as above occurs even when a lenticular lens is used.
A method of displaying a 3-dimensional image using line light sources, without using a parallax separation unit, is also widely known in the art (U.S. Pat. No. 5,897,184). However, this method also has the problems of the 3-dimensional image obtained by the parallax separation unit.